Least Reliable Water Systems in America — 2026

Out of 0 ZIP codes with data across all 50 states, these are the lowest-ranked areas for reliability score. Each ZIP links to a full safety report with water quality, lead, radon, and flood data.

0 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Reliability Score	Safety Score

Rankings by State

State	ZIP Codes Ranked

Methodology

Water system reliability scores (0-100) combine violation frequency, violation recency, resolution rate, and system size. Systems with repeated health-based violations and unresolved issues score lowest. The reliability score focuses specifically on the water utility performance, distinct from the broader Home Safety Score.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-08-31.

Frequently Asked Questions

What does a low water reliability score mean?

A low reliability score (below 50) indicates a water system with frequent violations, poor resolution rates, or recurring compliance issues. These systems may have aging infrastructure, inadequate treatment, or management challenges.

How is reliability different from Home Safety Score?

The reliability score focuses specifically on water utility performance. Home Safety Score model 4.0.0 separately combines SDWIS identity plus accepted ECHO SDWA lifecycle-based water compliance, the UCMR 5 PFAS MCL screen, EPA radon zone, and annual EPA AirData AQI. A ZIP can have a reliable water system while another modeled component is unfavorable or unavailable.